The Isaac Newton Telescope Monitoring Survey of Local Group Dwarf Galaxies. V. The Star Formation History of Sagittarius Dwarf Irregular Galaxy Derived from Long-period Variable Stars

Van Loon, Jacobus

Abstract

We conducted an optical monitoring survey of the Sagittarius dwarf irregular galaxy (SagDIG) during the period of 2016 June–2017 October, using the 2.5 m Isaac Newton Telescopeat La Palama. Our goal was to identify long-period variable stars (LPVs), namely, asymptotic giant branch stars (AGBs) and red supergiant stars, to obtain the star formation history of isolated, metal-poor SagDIG. For our purpose, we used a method that relies on evaluating the relation between luminosity and the birth mass of these most evolved stars. We found 27 LPV candidates within 2 half-light radii of SagDIG. 10 LPV candidates were in common with previous studies, including one extreme-AGB (x-AGB). By adopting the metallicity Z = 0.0002 for older populations and Z = 0.0004 for younger ages, we estimated that the star formation rate changes from 0.0005 ± 0.0002 M? yr-1 kpc-2 (13 Gyr ago) to 0.0021 ± 0.0010 M? yr-1 kpc-2 (0.06 Gyr ago). Like many dwarf irregular galaxies, SagDIG has had continuous star formation activity across its lifetime, though with different rates, and experiences an enhancement of star formation since z ? 1. We also evaluated the total stellar mass within 2 half-light radii of SagDIG for three choices of metallicities. For metallicity Z = 0.0002 and 0.0004, we estimated the stellar mass M* = (5.4 ± 2.3) × 106 and (3.0 ± 1.3) × 106 M?, respectively. Additionally, we determined a distance modulus of µ = 25.27 ± 0.05 mag, using the tip of the red giant branch.

Citation

Van Loon, J. (2023). The Isaac Newton Telescope Monitoring Survey of Local Group Dwarf Galaxies. V. The Star Formation History of Sagittarius Dwarf Irregular Galaxy Derived from Long-period Variable Stars. Astrophysical Journal, https://doi.org/10.3847/1538-4357/aca471

• Acceptance Date: Nov 17, 2022
• Publication Date: Jan 4, 2023
• Journal: The Astrophysical Journal: an international review of astronomy and astronomical physics
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• DOI: https://doi.org/10.3847/1538-4357/aca471
• Publisher URL: https://iopscience.iop.org/article/10.3847/1538-4357/aca471